title: In-phase alignments of asymmetric building units in Ln4GaSbS9 (Ln = Pr, Nd, Sm, Gd-Ho) and their strong nonlinear optical responses in middle IR.
abstract: New noncentrosymmetric rare-earth metal gallium thioantimonates, Ln(4)GaSbS(9) were synthesized from stoichiometric element mixtures at 950 °C by high-temperature solid-state reactions. These compounds crystallize in orthorhombic space group Aba2 (no.41) with a = 13.799(3)-13.427(5) Å, b = 14.187(3)-13.756(5) Å, c = 14.323(3)-13.954(5) Å, V = 2804(2)-2577 (2) Å(3), and Z = 8 on going from Ln = Pr to Ho. The asymmetric building units, bimetallic polar (Sb(2)S(5)) units, and dimeric (GaS(4))(2) tetrahedra are in-phase aligned as an infinite single anionic chain of {[(Ga(2)S(6))(Sb(2)S(5))](10-)}(∞) that is further packed in a noncentrosymmetric pseudolayer motif perpendicular to the c axis. Three of the title compounds show large powder second harmonic generation (SHG) effects at 2.05 μm, and two of them also exhibit large transparency ranges (1.75 or 0.75 to 25 μm) in the middle-IR region. Significantly, the Sm-member exhibits the strongest SHG response among sulfides to date with intensity approximately 3.8 times that of the benchmark AgGaS(2). The band structures, indirect band gap nature, bonding strengths, and lone pair effects around Sb have also been studied by Vienna ab initio simulation package calculations.
authors.affiliation: Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China.
authors.forename: Mei-Chun
authors.initials: MC
authors.lastname: Chen
authors.forename: Long-Hua
authors.initials: LH
authors.lastname: Li
authors.forename: Yu-Biao
authors.initials: YB
authors.lastname: Chen
authors.forename: Ling
authors.initials: L
authors.lastname: Chen
mesh_terms: D000965:Antimony / Q000737:chemistry*; D005708:Gallium / Q000737:chemistry*; D007259:Infrared Rays; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008958:Models, Molecular; D055095:Optics and Photonics; D013455:Sulfur / Q000737:chemistry*
chemical_list: D028581:Lanthanoid Series Elements; D013455:Sulfur; D000965:Antimony; D005708:Gallium